A horizontal rotary hook providing an easy replacement of a bobbin has conventionally been used in sewing machines. The horizontal rotary hook comprises an outer rotating hook having an annular sliding surface formed on an upper surface of outer peripheral wall thereof and an inner bobbin case holder accommodating a thread bobbin therein and supported in the rotating hook so as to be rotatable relative to the sliding surface. The rotating hook is adapted to be rotated in a predetermined direction by a sewing machine motor or the like while the bobbin case holder is prevented from rotation relative to a sewing bed of the sewing machine.
The bobbin case holder is made of a synthetic resin so that a reduction is achieved in the weight and production cost thereof. Furthermore, the rotating hook has also been made of a synthetic resin recently. In this case, a beak is provided on an outer peripheral wall of the rotating hook for seizing a loop of bobbin thread. A beak member constituting the beak has been proposed to be separated from a rotating hook body. For example, JP-A-H07-31775 discloses a horizontal rotary hook in which a beak member is made of a metal, is separate from the rotating hook and is mounted on an inner peripheral surface of an outer peripheral wall of the rotating hook made of the synthetic resin. Furthermore, the beak member has also been proposed to be made of a synthetic resin for the purpose of further reduction in the production cost.
However, a high dimensional accuracy cannot always be obtained when the beak member is made of a synthetic resin by injection molding. As a result, there is a possibility that the beak member may collide against a protrusion such as a thread guide of the bobbin case holder during rotation of the rotating hook and accordingly, the rotating hook may not be rotated smoothly. In view of this problem, when the beak member is made of a synthetic resin, fine finishing such as cutting and/or polishing is necessitated for the beak after the molding of the beak member. Thus, the production cost cannot effectively be reduced.